Polymerization process for butene-1 and alpha-olefin monomers

ABSTRACT

It is herein disclosed, a process for polymerizing butene-1 into homopolymers and copolymers, using a catalyst system containing titanium trichloride, diethylaluminum chloride, and a substituted phenol in specified molar proportions. It is further disclosed, products made by the inventive process, and articles of manufacture made from these products.

BACKGROUND OF THE INVENTION

This invention generally relates to polymerization. It is moreparticularly concerned with a process for polymerizing novelhomopolymers or copolymers from monomers of butene-1 and one or more ofa variety of alpha-olefins having 2-10 carbon atoms preferably includingethylene, propylene, and mixtures thereof, which involves a criticalselection of reaction conditions, reactants, reactant properties, andcatalyst components.

As is well known to those familiar with the art, butene-1 and propylenecan each be homopolymerized into crystalline polymers. Such homopolymershave been produced with an isotactic index (measured as the weightpercent insoluble in boiling diethyl ether) in the order of 95-98.

The resultant polybutene-1 has two major crystalline forms. Upon coolingfrom the melt, there is formed a metastable crystalline modificationknown as "Form II." Over a period of time, usually several days, theForm II modification transforms into a stable modification known as"Form I." The transformation from Form II to Form I is accompanied bydimensional change in the polymer. The dimensional instability ofpolybutene-1 renders it disadvantageous for many applications. Forexample, films which are initially clear lose their optical clarity asthe polymer changes crystalline form. Known processes for polymerizingbutene-1 are taught in a variety of patents including U.S. Pat. No.3,464,962 assigned to Mobil.

The current process allows for polymerization of 1-butene homopolymersor copolymers of butene-1 and ethylene at temperatures from 130° F. to160° F. using a catalyst consisting of titanium trichloride,diethylaluminum chloride, and diethyl aluminum iodide where the molarratio of aluminum to titanium is between 2:1 and 4:1 and the molar ratioof diethylaluminum chloride to diethylaluminum iodide is 1:1 to 3:1.

The problems with the current process include: (1) low catalyst activitywhich limits rates due to the deashing step; (2) effluent toxicity; and(3) slow crystallization transformation rate.

A new process for polymerizing butene-1 has been discovered whichinvolves a critical selection of reaction conditions, reactantproportions, and catalyst components.

The process without iodide produces butene-1 polymers with a higherdegree of crystallinity than those made with the aluminum diethylchloride/aluminum diethyl iodide as the cocatalyst.

Accordingly, it is a broad object of this invention to provide a newprocess for producing such butene-1 homopolymers and copolymers byutilizing a more economical and an environmentally safer polymerizationprocess which prevents iodide from getting into the waste streams.

SUMMARY OF THE INVENTION

This invention provides a method for producing homopolymers andcopolymers of butene-1 that comprises copolymerizing a monomer ormixture of monomers, such as butene-1 and one or more alpha-olefinshaving 2-10 carbon atoms preferably including ethylene, propylene, andmixtures thereof at a temperature of between about 130° F. and about150° F., in the presence of a catalyst system consisting essentially oftitanium trichloride, and a cocatalyst which is a mixture of substitutedphenol and diethylaluminum chloride wherein the mole percent ratio ofdiethylaluminum chloride to substituted phenol is between about 4:1 andabout 0.5:1 and the molar ratio of aluminum to titanium is between 3:1and 6:1.

The invention further provides products made by the inventive process,and articles of manufacture made from these products.

DETAILED DESCRIPTION OF THE INVENTION

The resultant butene-1 homopolymers and copolymers of this inventionhave the desirable outstanding physical characteristics of toughness,good stress-crack properties, and high oxygen permeability. They haveX-ray and infrared patterns typical of polybutene-1 homopolymer in theForm I crystalline modification and the present invention's method formaking these polymers is now more economical and environmentally safer.

Upon cooling some of the copolymers of this invention from the melt(i.e., molten state), they transform extremely rapidly from Form II intostable Form I. In fact, Form II is usually virtually undetectable.Consequently, they are dimensionally stable and undergo no furthercrystalline change and, therefore, only a minimum post-crystallizationis observed. The amount of post-crystallization is less than 0.5 percentby weight, as measured, over a 24-hour period, in a density gradientcolumn, wherein the weight percent change of density of the polymer ismeasured as a function time.

The homopolymers and copolymers of this invention have a tensilemodulus, determined by ASTM method D638 using a D412 sample, greaterthan 25,000 psi, usually between about 25,000 and about 35,000 psi.

The homopolymers and copolymers prepared by this unique method haveoutstanding electrical insulating properties, toughness, andflexibility. Accordingly, they are suitable for use in wire and cableinsulation, plastic pipes, films, coatings, heavy duty bags, food wraps,and other applications, either by themselves or blended with otherpolymers.

The unique method of the present invention involves several criticalfactors that must be carefully controlled. These factors are thecomponents of the catalyst composition, and the reaction conditions. Thepolymerization can be carried out in batch operation or in a continuousoperation.

The monomers used in the novel method are butene-1 or with one or moreof a variety of alpha-olefins having 2-10 carbon atoms preferablyincluding ethylene, propylene, and mixtures thereof. Thecopolymerization process of this invention is carried out attemperatures of between about 130° F. and about 150° F. The contacttime, or the average residence time in continuous operation is betweenabout 1 hour and about 5 hours.

The catalyst system used in the process for producing the copolymers ofthis invention consists essentially of titanium trichloride, substitutedphenol e.g. BHT, and diethylaluminum chloride. The molar ratio ofdiethylaluminum chloride to substituted phenol will be between about 4:1to 0.5:1. The molar ratio of aluminum to titanium in the catalyst systemwill be between 3:1 and 6:1.

It is essential that the cocatalyst used herein is a mixture ofdiethylaluminum chloride (DEAC) and substituted phenol, for example,butylated hydroxytoluene (BHT). The use of substituted phenol alone withtitanium trichloride (TiCl₃) results in a catalyst system of lowactivity. When only diethylaluminum chloride is used in the catalystsystem, the polymers produced have a low tensile modulus.

Butylated hydroxytoluene (BHT) useful in the practice of this inventionis 2,6-di-ter-butyl-p-cresol. It can be represented by the chemicalformula (C₁₈ H₃₇)₂ CH₃ C₆ H₂ OH. It is commonly used as an antioxidantor heat stabilizer for polyolefins, such as polypropylene.

A preferred polymerization of butene-1 with propylene is demonstrated inthe following examples.

EXAMPLES 1 to 5

A series of batch bulk polymerization runs were made using a charge feedcontaining 7 mole percent propylene, the balance being butene-1. Allruns were carried out at 150° F. for one hour, except for Example 5which was carried out at 140° F. for two hours. In each run, thecatalyst system was titanium trichloride and diethylaluminum chlorideand substituted phenol, in which the aluminum to titanium molar ratioand the molar ratio of DEAC t0 substituted phenol were varied. Pertinentdata and results of these runs are set forth in Table I.

                  TABLE I                                                         ______________________________________                                                                          Wt.                                                                           Percent                                                                              Tensile                              Ex-   DEAC/    Al/    Temp. Time, Density                                                                              Modulus                              ample BHT.sup.1                                                                              Ti.sup.2                                                                             °F.                                                                          Hours Change psi                                  ______________________________________                                        1     4        3      150   1     0.21   25,500                               2       1.5    6      150   1     0.27   20,600                               3       2.45   4      150   1     0.27   17,500                               4     2        4      150   1     0.29   19,400                               5     4        3      140   2     0.25   30,000                               ______________________________________                                         .sup.1 Molar ratio of diethylaluminum chloride to substituted phenol          (BHT).                                                                        .sup.2 Molar ratio of aluminum to titanium.                              

As has been mentioned hereinbefore, some general considerations shouldbe observed when operating within the aforedescribed ranges ofconditions. When operating at temperatures of about 150° F., an aluminumto titanium molar ratio of about 3:1 is favored on short runs. (SeeExample 1, showing significant improvement in tensile modulus and inweight percent density change.) Usually though, higher molar ratios ofdiethylaluminum chloride to substituted phenol, approaching 4:1, arepreferred. Using an aluminum to titanium molar ratio of 3:1 and a higherthan 4:1 molar ratio of diethyl-aluminum chloride to substituted phenol,temperatures as low as 130° F. can be used effectively.

EXAMPLES 6 to 12

A series of batch bulk polymerization runs were carried out, varying themole percent propylene in the butene-1 feed for each run. In each run,the catalyst components were titanium trichloride and a mixture of 80mole percent diethylaluminum chloride (DEAC) and 20 mole percentbutylated hydroxy toluene (BHT) (molar ratio of 4:1), wherein the molarratio of aluminum to titanium was 3:1. Each run was carried out 50° F.for one hour.

For each polymer product, the weight percent density change over a24-hour period and the tensile modulus were determined. The pertinentdata for each run are set forth in

                  TABLE II                                                        ______________________________________                                                            Wt.                                                                           Percent   Tensile                                         Feed, mole percent  Density   Modulus                                         Example                                                                              Butene-1  Propylene  Change  psi                                       ______________________________________                                        6      100       0                  33,300                                    7      98        2          1.85    41,000                                    8      97        3          1.39    39,600                                    9      96        4          0.96    38,000                                    10     95        5          0.40    33,300                                    11     94        6          0.23    29,100                                    12       90.4      9.6      --      21,400                                    ______________________________________                                    

From Table II, it will be noted that, as increasing amounts ofpolypropylene are used in the feed, the tensile modulus of the polymerincreases, from 100% butene-1 to a maximum at about 2% propylene andthen decreases. At between about 8% and 9% propylene, the tensilemodulus has decreased to about 25,000 psi. Above about 9% propylene, thetensile modulus is well below the acceptable minimum of 25,000 psi forheavy duty purposes. Together with a high tensile modulus of at leastabout 25,000 psi, a copolymer of this invention must have dimensionalstability, as evidenced by a post-crystallization of below about 0.5weight percent.

Although the aforedescribed ranges of propylene content in the feed havebeen determined upon the basis of one set of reaction conditions, theyare applicable to polymerization reactions carried out at otherconditions within the ranges set forth hereinafter. When operatingwithin these ranges of conditions, however, certain generalrelationships among the conditions should be observed, in order toachieve the production of the novel modulus and dimensional stability.These relationships are described and illustrated hereinafter.

EXAMPLES 13 to 18

A series of batch bulk polymerization runs were carried out at about140° F. for one hour. In each run, the charge feed was a mixture of 8mole percent propylene and 92 percent butene-1. In each run, thecatalyst system was titanium trichloride and diethylaluminum chlorideand substituted phenol (BHT), in which the aluminum to titanium molarratio and the molar ratio of diethylaluminum dichloride to diethylaluminum iodide were varied. Pertinent data and results of these runsare set forth in Table III.

                  TABLE III                                                       ______________________________________                                                                    Wt.                                                                           Percent                                                                              Tensile                                             DEAC/              Density                                                                              Modulus                                    Example  BHT.sup.1                                                                              Al/Ti.sup.2                                                                             Change psi                                        ______________________________________                                        13       2.45     3         0.20   25,500                                     14       2.45     4         0.30   26,900                                     15       2.45     5         0.10   30,300                                     16       2.45     6         0.22   26,000                                     17       2        4         0.22   27,500                                     18       2        6         0.21   29,700                                     ______________________________________                                         .sup.1 Molar ratio of diethylaluminum chloride to substituted phenol          [BHT].                                                                        .sup.2 Molar ratio of aluminum to titanium.                              

EXAMPLES 19 through 27

When operating on longer batch runs or at correspondingly longerresidence times in continuous operation, aluminum to titanium molarratios of between 4:1 and 6:1 are most feasible. This concept isdemonstrated by the following examples.

A series of batch bulk polymerization runs were carried out attemperatures of about 140° F. or about 150° F. for four hours, exceptfor Example 19 which was run for three hours. In each run, the chargefeed was between 7-8.5 mole percent propylene, the balance beingbutene-1. In each run, the catalyst system was titanium trichloride anddiethylaluminum chloride and substituted phenol (BHT), in which thealuminum to titanium molar ratio and the molar ratio of diethylaluminumchloride to BHT were varied. Pertinent data and results of these runsare set forth in Table IV.

                  TABLE IV                                                        ______________________________________                                              Mole                                                                          Per-                        Wt.                                               cent                        Percent                                                                              Tensile                              Ex-   Pro-    DEAC/    Al/  Temp. Density                                                                              Modulus                              ample pylene  BHT.sup.1                                                                              Ti.sup.2                                                                           °F.                                                                          Change psi                                  ______________________________________                                        19    8       4        3    150   0.62   21,300                               20    7       4        6    150   0.47   29,700                               21    7       1.5      6    150   0.31   29,900                               22    7       1.5      6    140   0.18   32,000                               23    8       1.5      6    140   0.24   32,600                               24      8.5   0.67     6    140   0.27   26,600                               25      8.5   1.5      4    140   0.27   26,600                               26    8       0.67     4    140   0.18   29,600                               27    8       0.67     4    150   0.22   25,600                               ______________________________________                                         .sup.1 Molar ratio of diethylaluminum chloride to substituted phenol          (BHT).                                                                        .sup.2 Molar ratio of aluminum to titanium.                              

Although polymerization temperatures of about 150° F. can be used,higher tensile moduli are usually achieved when operating at about alower temperature, for example 140° F. (compare Example Nos. 21 vs. 22and Nos. 26 vs. 27).

EXAMPLE 28

A polymerization run was carried out in a continuous bulk polymerizationunit. Rigorously anhydrous conditions were maintained. The charge was amixture of 91.5 mole percent butene-1 and 8.5 mole percent propylene.The catalyst components were titanium trichloride and a mixture of 60mole percent diethylaluminum chloride and 40 mole percent substitutedphenol. The catalyst components were added at a rate to maintain a molarratio of aluminum to titanium of 6:1. The copolymerization was carriedout at a temperature of 140° F. The rate of addition of olefin monomerswas adjusted to maintain an average residence time of 3.7 hours andcopolymers product was continuously removed. Throughout the run thecopolymer produced had the following characteristics:

    ______________________________________                                        Isotactic index (percent insoluble in boiling                                                        95-98                                                  diethyl ether)                                                                Tensile modulus (ASTM D638) psi                                                                         28-32,000                                           Post-crystallization, wt. percent                                                                    0.2-0.4                                                Density, g/cc          0.905-0.908                                            Brittleness temp.      -23° C.                                         ______________________________________                                    

It exhibited X-ray and infrared pattern characteristics of Form Ipolybutene-1.

EXAMPLE 29

A continuous bulk polymerization run was carried out as described inExample 28, except that the feed contained 8 mole percent propylene and92 mole percent butene-1. The polymer produced had the following averageproperties:

    ______________________________________                                        Isotactic index (percent insoluble in boiling                                                            95                                                 diethyl ether                                                                 Tensile modulus (ASTM D638) psi                                                                          28,500                                             Post-crystallization, wt. percent                                                                        0.3                                                Density, g/cc              0.9072                                             ______________________________________                                    

EXAMPLE 30

A continuous bulk polymerization run was carried out as described inExample 28, except that the feed contained 7 mole % propylene and 93mole % butene. The polymerization temperature was 150° F., the aluminumto titanium molar ratio was 3:1, and the diethylaluminum chloride tosubstituted phenol molar ratio was 4:1. The tensile modulus of thepolymer product was only about 16,900 psi, although the weight percentpostcrystallization was 0.45.

As in any stereospecific process of this type, anhydrous conditions mustbe maintained and air and oxygen must be excluded. This is accomplishedconventionally by operating the process under an atmosphere of inertgas, such as nitrogen. If it is desired to control the molecular weightof the copolymer, conventional materials for this purpose, such ashydrogen and carbon dioxide, can be added to the reaction system.Deactivation and removal of catalyst components from the reactoreffluent and copolymer product recovery are effected by any of thevarious means well known to those skilled in the art.

The runs described in the foregoing specific working examples have beencarried out using bulk polymerization techniques, i.e., without the useof solvents or slurrying media other than the 1-olefins charged, both inbatch and in continuous operations.

EXAMPLE 31

A polymerization run was carried out in a 1-liter glass reactor. Thereactor was charged with 600 ml of n-heptane under rigorously anhydrousconditions. The reactor was then pressurized with butene-1 to a pressureof 873 mm mercury at 150° F. hen 125 ml of additional n-heptane wereadded to the reactor followed by the addition of propylene until theequilibrium pressure was reached at 150° F. The feed contained 7.4 molepercent propylene and 92.6 mole percent butene-1. A catalyst systemconsisting of 0.247 g titanium trichloride and 1.9 cc of a mixture ofdiethylaluminum chloride and substituted phenol in a mole ratio of 4:1was then flushed into the reactor with 75 ml of n-heptane. The reactionmixture was then stirred vigorously for a period of two hours at 150°F., during which time the pressure in the reactor had dropped to 392 mmmercury. Nitrogen was introduced into the reactor to increase thepressure to 403 mm. The reactor was continued for 40 additional minutesat 150° F., after which time it was quenched with methanol. Thecopolymer product had a post-crystallization of about 0.3 weightpercent. No differences in properties between the copolymer of thisexample and a copolymer produced by bulk polymerization from acomparable feed composition could be observed.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be resorted to, without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand.

What is claimed is:
 1. A method for producing butene-1 polymers thatcomprises polymerizing(a) butene-1 or a monomer mixture of butene-1 andone or more alpha-olefins having 2-10 carbon atoms; (b) at a temperaturebetween about 130° F. and about 150° F.; and (c) in the presence of acatalyst system consisting essentially of titanium trichloride, and acocatalyst which is a mixture of diethylaluminum chloride and at leastone substituted phenol and wherein the mole percent. ratio ofdiethylaluminum chloride to said substituted phenol is between about 4:1and 0.5:1, and the molar ratio of aluminum to titanium is between about3:1 and about 6:1.
 2. A method as in claim 1 wherein(a) said temperatureis about 140° F.; (b) said mole percent ratio of diethylaluminumchloride to said substituted phenol is about 2.45:1; and (c) said molarratio of aluminum to titanium is about 5:1.
 3. A method as in claim 1wherein(a) said temperature is about 140° F.; (b) said mole percentratio of diethylaluminum chloride to said substituted phenol is about1.5:1; and (c) said molar ratio of aluminum to titanium is about 6:1. 4.A method as in claim 1 wherein(a) said temperature is about 140° F.; (b)said mole percent ratio of diethylaluminum chloride to said substitutedphenol is about 0.67:1; and (c) said molar ratio of aluminum to titaniumis about 4:1.
 5. A method as in claim 1 wherein(a) said temperature isabout 150° F.; (b) said mole percent ratio of diethylaluminum chlorideto said substituted phenol is about 1.5:1; and (c) said molar ratio ofaluminum to titanium is about 6:1.
 6. A method as in claim 1 whereinsaid alpha-olefin monomer is selected from the group consisting ofethylene, propylene, and mixtures thereof.
 7. A method as in claim 6wherein said alpha-olefin monomer is ethylene.
 8. A method as in claim 7wherein said alpha-olefin monomer is propylene.
 9. A product produced bythe process of claim
 1. 10. A shaped article of manufacture producedfrom the product of claim 9.